4KQ runs rough when cold...

[Frank de Kat]

>Date: Thu, 28 Dec 2000 23:24:25 -0500
>To: z
>From: Frank de Kat <fdekat at sentex.net>
>
>
>Message: 10
>From: Bill Phelps <wphelps at rizzo.com>
>To: "'quattro at audifans.com'" <quattro at audifans.com>
>Subject: 4KQ runs rough when cold...
>Date: Wed, 27 Dec 2000 16:40:46 -0500
>
>
>I've notice recently that after starting my 87 4KCSQ in the cold weather, it
>runs a bit rough for the first minute or so. The car starts fine and idles
>fine, but if you press the accelerator too soon it chugs a bit. Once it
>warms up, the car runs great. I know German cars run a bit rough when cold,
>but I have not noticed this problem in this car before.
>
>Within the last two years all of the normal "tune up" stuff has been done
>including the plugs, wires, dist. cap and rotor, fuel pump, fuel filters
>(both of em), all vac hoses and stuff are good too.
>
>
>Any ideas? Cold start injector?
>
>
>
>Thanks..
>
>
>Bill

I've just had the same problem, on a 4Kq.
The car was acting lie the choke was not on if it was cold (If it had a carb).
Turns out it was the coolant temperature snesor. It did not go to a high
resistance value when the coolant  was cold, so the computer never though
the motor was cold, so it never richened the mixture when starting.
This sensor is the lower one, on the upper hose where it goes into the block.
On a good sensor, I got about 2500 ohms cold, and about 300 ohms warm.

Regards...

Frank de Kat 
fdekat at sentex.net   
Dundas, Ontario, Canada

Audi 4000CSq (x2 !)
http://www.sentex.net/~fdekat
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